1. Field of the Invention
The present invention relates to a grommet which holds a wire harness having a route that penetrates an opening in a panel, particularly an opening in a vehicle panel, etc.
2. Description of Background Information
Wire harness arrangement routes for vehicles have recently become more complicated and versatile as mounting of various electrical components on vehicles advances. This requires a wide use of parts for wire harness protection or maintenance, such as harness protectors for avoiding interference with peripheral parts and grommets used for penetrating through the openings provided in a vehicle panel.
In particular, via an opening which is formed in a vehicle panel, a grommet formed of integrally molded rubber, etc. is generally used on a wire harness having a route, for instance, from an engine compartment to a passenger compartment or from a vehicle body to door areas, for the purpose of holding a cable arrangement route and avoiding contact with the vehicle panel and resulting damages. For example, as shown in FIG. 7, a conventional grommet 10f to be mounted on a wire harness 16, which is arranged to penetrate a vehicle panel 20, includes wire harness holding areas 11 and 12 for engaging around and tightly holding the outer periphery of the harness. An engagement area 13 is provided for fixedly engaging the grommet 10f to a predetermined opening formed in the vehicle panel, and a tapered area 14 connects the wire harness holding area 11 and the engagement area 13 over a near-conical tapered area. In this case, the grommet 10f is connected to the wire harness 16 by means of fixing tapes 17 and 18 at the respective wire harness holding areas 11 and 12.
The description which follows makes reference to FIGS. 8(a) and 8(b) regarding an insertion operation and an engaged condition relative to a panel opening in accordance with the conventional grommet 10f.
As shown in FIG. 8(a), when the grommet 10f, which is fixedly connected to a wire harness 16, is drawn in an insertion direction, via an opening from one side (a left side as shown in the drawing) of a vehicle panel 20, by taking a wire harness holding area side (left direction in the drawing) provided on the tapered area 14 as an inserting direction, an insertion resistance arises as a result of sliding contact at the edge areas between the tapered area 14 and an opening 21. Therefore, by further drawing the grommet 10f with a force greater than the insertion resistance, applied in the direction shown by the arrow designated F3, the engagement area 13 is fixedly engaged in the opening 21 as shown in FIG. 8(b), and a predetermined route is maintained, without harness 16 making contact with the opening 21.
With the conventional grommet 10f, there was a problem of considerable worsening of the mounting workability of the wire harness 16 due to an insertion resistance becoming greater as a result of sliding contact with the surface of the tapered area 14 over the entire area by the edge of the opening 21 during insertion of the grommet and harness into the opening 21.
In addition, another factor increasing the insertion resistance includes the use of material having a higher deformability which lacks surface slidability such as the integrally molded rubber of the grommet 10f, which further increases the frictional resistance with the edge area of the opening 21, thereby necessitating a greater drawing force F3.
One known solution to this problem is shown in the Japanese unexamined Patent Publication No. (Hei) 7-115286. Such a method as reducing a frictional resistance, or insertion resistance, by applying many minute concave/convex areas on the surface of a tapered area, namely, applying a electrical discharge process, thereby making a contact area with an edge area smaller at insertion when inserting the work into the opening.
According to this known solution, a method for forming concave/convex areas on the mold die by electrical discharge machining is generally utilized to form a plurality of concave/convex areas on the tapered surface of the grommet formed from integrally molded rubber, thus forming concave/convex areas on the tapered area formed on the integrally molded rubber grommet. However, the electrical discharge machine has an extremely slow processing speed compared with the case of using normal NC processing (mechanical processing by use of cutting tools), and a problem of higher processing cost.
An objective of the present invention is to provide a grommet that allows easy engagement by reducing an insertion resistance during insertion of the grommet into the opening of vehicle panel, thereby providing a grommet capable of reducing the machining cost for molding dies as well as the machining time.